When I think of an NDA, I always think of the Krabby Patty formula. Mr. Krabs kept what he wanted to himself inside a bottle in his safe. Everything else that was common, he didn’t care about. The same goes for a company and an NDA. The NDA will have specific things that they either have not patented yet, can’t stop other people from using (like a recipe) etc. You don’t want to go overboard with an NDA, however. The person that gets the preview of a product you are creating will build “hype” for you. You need them to be able to talk about some aspects of the product, but not enough that another company can replicate the product (and possibly begin selling it before or shortly after you do)